1. Field of the Invention
This disclosure relates to the field of elliptical exercise machines. In particular, to elliptical exercise machines which allow for alteration in the shape of the foot path.
2. Description of the Related Art
The benefits of regular aerobic exercise on individuals of any age is well documented in fitness science. Aerobic exercise can dramatically improve cardiac stamina and function, as well as leading to weight loss, increased metabolism and other benefits. At the same time, aerobic exercise has often been linked to damaging effects, particularly to joints or similar structures where the impact from many aerobic exercise activities causes injury. Therefore, those involved in the exercise industry are continuously seeking ways to provide users with exercises that have all the benefits of aerobic exercise, without the damaging side effects.
Most low-impact aerobic exercises have traditionally been difficult to perform. Many low-impact aerobic exercises (such as those performed in water) traditionally require performance either outside or at a gym. Cold weather, other undesirable conditions, and cost can make these types of aerobic exercise unobtainable at some times and to some people. In order to allow people to perform aerobic exercises without having to go outside or to gyms or the like, fitness machines have been developed to allow a user to perform aerobic exercises in a small area of their home.
Many of these machines, however, suffer from either being relatively high-impact, or from being complicated to use and understand. In either of these cases, the fitness machine often becomes a coat rack instead of being used for its intended purpose. Recently, a class of machines which are referred to as “elliptical machines” or “elliptical cross-trainers” have become very popular due to their ease of use and their provision of relatively low-impact aerobic exercise.
Generally in these types of machines, a user performs a motion using their legs that forces their feet to move in a generally elliptical motion about each other. This motion is designed to simulate the motion of the feet when jogging or climbing but the rotational motion is “low-impact” compared to jogging or climbing where the feet regularly impact a surface. In an elliptical machine, a user uses a natural walking motion to instead move their feet through the smooth exercise pattern dictated by the machine. This motion may also be complemented by them moving their arms in a reciprocating motion while pulling or pushing various arms on the machine whose motion is connected to the motion of the feet, and vice-versa.
Currently, the biggest problem with elliptical machines is that the dimensions of the ellipse made by the user's feet are generally severely limited in size and shape by the design of the machine. The ellipses generated by these machines are often created by the interaction of a plurality of different partial motions, and attempts to alter the motion of a user in one dimension generally also alters the motion in another. It is desirable that users have the option to arrange the machine so that the ellipse can be tailored to fit their stride, but with machines on the market today, that generally is not possible.
The problem is most simply described by looking at the elliptical motion the feet make when using an elliptical exercise machine. This elliptical motion can be described by the dimensions of the ellipse. Since users generally stand upright on elliptical machines, the user's feet travel generally horizontally relative to the surface upon which the machine rests. This represents the users stride length or how far they step. Further, the user's feet are raised and lowered relative to the surface as they move through the ellipse. This is the height to which the user's feet are raised. How a user steps depends on the type of action they are performing. A more circular ellipse will often correspond more to the motion made while climbing, a slightly more elongated ellipse is more akin to walking, while a significantly elongated ellipse can be more akin to the motion of running.
Even within this limited framework, however, each user's stride length is different. A very short person will generally want all the dimensions of the ellipse to be smaller than someone who is very tall or has particularly long legs. In an elliptical machine, it therefore desirable that the length of the machine's “stride” correspond to the particular stride length of that user. Further, as a user's speed on the machine increases or decreases or as the resistance imparted by the machine increases or decreases, it can be desirable for the machine to alter the type of stride the user is making (by elongating or shortening the stride) to better correspond to a more natural movement.
In elliptical machines currently, the size and shape of the ellipse is generally fixed by the construction of the machine. That is, the footrests (the portion of an elliptical machine that will traverse the same ellipse as the user's feet) are generally forced to proscribe only a single ellipse when the machine is used and that ellipse is generally unchangeable. Some machines allow for some alteration of this ellipse, but generally those machines increase both dimensions of the ellipse, not just the horizontal component. That is, the user can adjust the total size of the ellipse, but the ratio of the ellipse's components always remains relatively constant.
This arrangement means that many users are not comfortable with the stride of an elliptical machine as it is either too long or too short for their stride. Even if the stride is adjustable, the user may still be uncomfortable. For some users, the stride will be much too short compared to their normal stride and attempts to increase the stride length result in their feet being raised uncomfortably high (e.g. turning a walking or jogging exercise motion into more of a climbing motion), while for others the same machine's stride can be much to long (resulting in overstretching of their legs as if they are running all the time). Further, a user may desire to tailor the machine's motion for the general type of exercise they want to perform (e.g., more jogging motion or more climbing motion) and may wish to alter the motion during an exercise session to have a more varied workout.